The present invention relates to a process for the sealing and internal repair of systems of laid conduits having a small internal diameter, in which sealing is carried out by blocking a leak by means of an introduced sealant and internal repair is carried out by abrasively blowing out and recoating of the conduit with resin material. Such conduits are, for example, feed and discharge conduits for water or gas in residential, industrial and municipal installations up to a diameter of about 200 mm; this includes domestic and industrialsewage conduits up to the mains.
The problem of damage and encrustation of such conduits has been known for along time. Such damage is due, among other things, to corrosion, movement and vibration of the earth round the conduits; encrustations are due, in particular, to lime deposits from the water, to rust formation in the conduit, to other deposits from the water, to reaction products between substances entrained in the water and the conduit metal etc. Combinations of the above-mentioned effects are also known.
This damage or these encrustations are particularly undesirable in the case of conduits which are fixed in a wall or laid in the ground; of course, conduits are usually laid in this manner nowadays.
Sealing and blocking techniques for laid conduits are also known from the patent literature:
U.S. Pat. No. 3,287,148 teaches a process for sealing laid gas conduits by blowing in a foamed sealing emulsion. The foam settles on the internal wall and condenses there. In the case of leaks, it tends to settle in larger quantities.
This method is expressly suited only to gas conduits; solid additions to the sealing emulsion are neither taught nor made obvious.
The process according to U.S. Pat. No. 3,727,412 describes a repair process in which the conduit portion with the leak is sealed at the front and rear. A specially stablised emulsion is then pressed in which issues at the leak, is destabilised there and coagulates so that the leak is sealed.
Actual solid sealing materials are not therefore pressed in and the vehicle is water, not gas.
U.S. Pat. No. 4,311,409 teaches the sealing of leaks in laid conduits by means of very fine substances having a high capillary action. The very fine substance is arranged externally at the leak and is watered there. The capillary pressure thus obtained counteracts the delivery pressure of the medium flowing in the conduit.
The very fine insulating material is laid onto the conduit from the exterior, after excavation of the leak (FIG. 1).
Finally, U.S. Pat. No. 4,503,613 describes a process and an apparatus for the internal repair of laid conduits by means of "plastic mist" conveyed in a gas stream. It cannot be seen clearly from the patent specification whether actual leaks are also sealed with it and, moreover, it does not appear immediately possible to produce the plastic mist.
Nowadays, laid utility conduits are also cleaned by means of compressed air with and without the addition of sand and reactive resins are also atomised by means of compressed air into conduits which have been precleaned in this way.
With a relatively known method,of cleaning on a practical basis, compressed air is charged from optionally travelling compressor installations via a distributor into the conduit to be cleaned. In a first phase, only air which has been heated by compression is predried. Sand is subsequently added in the air stream in a second phase. It is important that the air and sand mixture is guided with a spiral movement through the conduit; normal movement of the mixture is explicitly described as ineffective. In a third phase of the known process, a reactive resin is injected into the conduit and distributed therein, again by means of a spirally moved compressed air stream.
GB A 2 140 337 teaches such a process. A characteristic of this process is that both the cleaning stream and the resin through-put stream flow in a pulsating manner through the conduit to be repaired. Furthermore, the sizes and quantities of the abrasive particles added to the cleaning stream are not defined, and the addition of bonding agents with grain sizes which are also defined to the repair resin is not mentioned.